The present invention is generally related to methods, devices, and systems for controlling surgical fluid flows, often during treatments of an eye. In exemplary embodiments, the invention allows clearing of an occlusion in an aspiration conduit pathway during (for example) cataract surgery or the like, optionally by reversing a peristaltic aspiration pump, modulating a vent valve between the aspiration conduit pathway and an irrigation fluid source, or the like.
With age, clouding of the lens or cataracts are fairly common. Cataracts may form in the hard central nucleus of the lens, in the softer peripheral cortical portion of the lens, or at the back of the lens near the capsular bag. Cataracts can be treated by the replacement of the cloudy lens with an artificial lens. Phacoemulsification systems often use ultrasound energy to fragment the lens and aspirate the lens material from within the capsular bag. This may allow the capsular bag to be used for positioning of the artificial lens and for maintaining the separation between the anterior portion of the eye and the vitreous humor in the posterior chamber of the eye.
During cataract surgery and other therapies of the eye, accurate control over the volume of fluid within the eye is highly beneficial. For example, while ultrasound energy breaks up the lens and allows it to be drawn into a treatment probe with an aspiration flow, a corresponding irrigation flow may be introduced into the eye so that the total volume of fluid in the eye does not change excessively. If the total volume of fluid in the eye is allowed to get too low at any time during the procedure, the eye may collapse and cause significant tissue damage. Similarly, excessive pressure within the eye may strain and injure tissues of the eye.
While a variety of specific fluid transport mechanisms have been used in phacoemulsification and other treatment systems for the eyes, most aspiration flow systems can generally be classified in one of two categories: 1) volumetric-based aspiration flow systems using positive displacement pumps; and 2) vacuum-based aspiration systems using a vacuum source. Among volumetric aspiration systems, peristaltic pumps (which use rotating rollers that press against a flexible tubing to induce flow) are commonly employed. Cassette systems can be used to couple peristaltic pump drive rotors or vacuum systems of the surgical consoles to an eye treatment handpiece, with the flow network conduit of the cassette being disposable to avoid cross-contamination between different patients.
While existing cataract surgery devices, systems, and methods have proven highly effective and have helped numerous patients, still further improvements and refinements remain desirable. For example, both volumetric and vacuum-based aspiration remain (to varying degrees) subject to temporary blockage or occlusion of the aspiration flow. As ultrasound energy breaks up the lens structure within the eye, small and soft tissue particles are readily drawn into an aspiration port of the treatment probe. Unfortunately, larger and/or harder tissue particles may at least temporarily cover the aspiration port of the probe, impeding flow of material and fluids from the eye into the probe. The ultrasound energy transmitted by the probe, in combination with the aspiration pump, often (though not always) eventually break up the occluding particle and successfully withdraw the occlusive material into the probe and from the eye. Unfortunately, significant fluid pressure transients can occur during this process. While existing eye treatment systems have structures that can successfully clear many or all occlusions, known occlusion clearing approaches may actually increase pressure transients, and/or may rely on complex and costly system components. More generally, current occlusion clearing methodologies may have either a relatively slow response time or insufficient pressure control.
In light of the above, it would be advantageous to provide improved devices, systems, and methods for eye surgery. It would be particularly advantageous if these improvements allowed occlusions of an aspiration conduit pathway to be cleared without subjecting the eye to excessive pressure surges, serious underpressurization, or other undesired pressure excursions or transients. It would be particularly advantageous if these improvements could be provided without excessively increasing the complexity, cost, or difficulty in using these sophisticated eye treatment systems.